UNITED NATIONS, March 16 (Reuters) - The United States, France and Britain on Wednesday urged the U.N. Security Council to take swift action on a proposed no-fly zone over Libya, as Washington suggested it might have decided to back the plan.

The Security Council met through the day behind closed doors to discuss a draft resolution authorizing a no-fly zone to halt Libyan government air strikes on rebels. But some council members, including veto powers Russia and China, are either undecided or have doubts.

British, French and Lebanese envoys distributed the draft on Tuesday after the Arab League called on the council to approve a no-fly zone in Libya. [ID:nN15272223]

Libya's deputy U.N. envoy Ibrahim Dabbashi, whose denunciation of leader Muammar Gaddafi last month inspired dozens of similar defections by Tripoli's diplomats worldwide, said there was no time for delays as Gaddafi's forces continue to pummel rebel forces in the east.

"The international community has to act within the next 10 hours," said Dabbashi. [ID:nN16185074]

In remarks that suggested a reluctant Washington had now agreed to support the idea of a no-fly zone, U.S. Secretary of State Hillary Clinton said she was hopeful the council would take a vote on a Libya resolution no later than Thursday.

"We are moving as rapidly as we can in New York to see whether we can get additional authorization for the international community to look at a broad range of actions, not just a no-fly zone but other actions as well," Clinton told reporters in Cairo.

"We won't know until there is an actual vote. We're hoping that will be no later than tomorrow," she said.

THURSDAY VOTE?

Clinton told CBS television that the Arab League call for a no-fly zone had caused a "sea change" in thinking.

"For the Arab League to call for military action to protect civilians in Libya, against a member of the Arab League, was an extraordinary statement of leadership and real conviction," she said. "That has changed the thinking of a lot of people."

Washington had reacted cautiously to the calls for a no-fly zone over Libya, with some officials concerned it could be militarily ineffective or politically damaging. It has insisted Arab nations actively participate in any such zone over Libya.

French U.N. Ambassador Gerard Araud told reporters he had formally submitted the draft to the U.N. secretariat with a view to putting it to a vote on Thursday. He said council members could propose final amendments overnight.

Diplomats said Araud was trying to force a vote.

French President Nicolas Sarkozy wrote in a letter to the council that it was "high time for the international community ... to pull together ... and respond without delay to the urgent appeal of the League of Arab States."

"Together, we can save the martyred people of Libya," he said. "It is now a matter of days, if not hours. The worst would be that the appeal of the (Arab League) and the Security Council decisions be overruled by the force of arms."

Lebanese Ambassador Nawaf Salam urged the council to act before it was too late for a no-fly zone to have any impact. He cited a prediction by Gaddafi's son Saif al-Islam that the rebels would be defeated within two days.

"It is our hope that the Security Council will impose a no-fly zone quickly and prove him wrong," he said.

Salam said one concern raised by Germany and others -- the apparent clash between the Arab League's call for a no-fly zone and its opposition to foreign military intervention -- was not a contradiction. He said Arab nations would help enforce any no-fly zone authorized by the council.

"There will be a significant Arab participation," he said.

Clinton told CBS the Arabs should play a prominent role. "The Arab League statement, their very courageous stance, suggests that they know that they have to step up and lead and participate in any action that would be internationally authorized," she said.

The draft resolution, obtained by Reuters, says the council "decides to establish a ban on all flights in the airspace of (Libya) in order to help protect civilians."

It authorizes member states to "take all necessary measures to enforce compliance" and says countries implementing the ban would be doing so in cooperation with the Arab League and in coordination with U.N. Secretary-General Ban Ki-moon.

The draft also provides for expanding sanctions already slapped by the U.N. council on Libyan leaders on Feb. 26 -- including asset freezes, travel bans and an arms embargo -- to cover all assets abroad of the Gaddafi government. (Additional reporting by Arshad Mohammed in Cairo and David Morgan in Washington; editing by Mohammad Zargham)